fix: broken eip155 logic in aws signer

[xJonathanLEI]

Motivation

A recent PR (#2260) broke the AWS KMS signer. With the latest version, using the signer would either result in a panic (in debug mode, for subtraction overflow), or simply wrong signatures. Relevant code:

ethers-rs/ethers-signers/src/aws/utils.rs

Lines 43 to 56 in 16f9fab

	if check_candidate(sig, RecoveryId::from_byte(0).unwrap(), digest, vk) {
	EthSig { r, s, v: 0 }
	} else if check_candidate(sig, RecoveryId::from_byte(1).unwrap(), digest, vk) {
	EthSig { r, s, v: 1 }
	} else {
	panic!("bad sig");
	}
	}
	/// Modify the v value of a signature to conform to eip155
	pub(super) fn apply_eip155(sig: &mut EthSig, chain_id: u64) {
	let v = (chain_id * 2 + 35) + ((sig.v - 1) % 2);
	sig.v = v;
	}

Note that v is already the recovery ID. There's no need to subtract it by 1 (doing so when v is 0 panics). v can also only be 0 or 1, so there's also no need to mod by 2.

Solution

Just use v directly in apply_eip155.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[gakonst]

Oops

[gyuho]

Nice! Thanks for the fix @xJonathanLEI